The present invention is particularly useful for vacuum induction melting equipment wherein an induction coil surrounds a metal containing crucible mounted inside a vacuum chamber. Traditionally, power of about 3000 Hz or higher frequency is passed through the walls of the chamber by means of hollow copper tubes having cooling water running through their center.
The induction coil which surrounds the melting crucible or other apparatus is usually a helix of water cooled copper tubing. This coil is connected to the tubing coming through the furnace wall. Provision ordinarily must be made for motion of the crucible within the chamber, such as tilting or vertical motion, and for removal of the coil and its encaptured crucible from the furnace for maintenance or replacement. Thus, there must be a disconnect device capable of carrying high frequency electrical currents while avoiding water leaks. Most commonly, standard hydraulic hoses having stranded electrical wires in their interior are used as connectors. These tend to be large and bulky but have the advantage of being adaptable to misalignments and the like. When rigid connectors are used, with conventional pipe connecting fittings such as unions, leaks can occur unless alignment is correct. And such fittings are inherently incapable of allowing movement of the induction apparatus in the chamber when under a vacuum.
Of course, a great variety of switches and other disconnectable connections are known for use with high currents. But, few of these devices are constructed in such a manner as to be effective with high frequency induction currents (which induce heating of the parts) and also to be effective in a vacuum.